Disposable absorbent article comprising a durable hydrophilic core wrap

ABSTRACT

A disposable absorbent article comprising an absorbent core, the absorbent core comprising: (a) a storage layer; and (b) a durable hydrophilic fluid pervious core wrap, the core wrap surrounding at least a portion of the storage layer, said core wrap comprising: (i) a core wrap substrate; and (ii) a hydrophilicity boosting composition coated on the substrate, the hydrophilicity boosting composition comprising a hydrophilicity boosting amount of nanoparticles, wherein the nanoparticles have a particle size of from about 1 to about 750 nanometers. Methods of preparing disposable absorbent articles are also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/758,066 filed on Jan. 15, 2004, which claims the benefit of U.S.Provisional Application No. 60/446,311, filed Feb. 10, 2003, and thisapplication is a continuation-in-part of U.S. application Ser. No.10/060,708 filed on Jan. 30, 2002, which claims the benefit of thefiling date of U.S. Provisional patent application Ser. No. 60/265,013filed Jan. 30, 2001.

FIELD OF THE INVENTION

The present invention relates to disposable absorbent article comprisinga durable hydrophilic core wrap, and methods of producing same.

BACKGROUND OF THE INVENTION

Disposable absorbent articles such as diapers and adult incontinenceproducts are well known in the art. Such disposable articles collect andretain urine and fecal material deposited thereon by the wearer.

Nonwoven fabrics made of synthetic fibers and/or natural fibers arecommonly used in absorbent articles, for example, as topsheet materialor as core wrap to enclose the storage layer of the absorbent core. Suchnonwoven fabrics are usually hydrophobic. However, for many applicationsin hygiene products it is necessary to have hydrophilic nonwoven.Therefore the nonwoven fabric has to be treated accordingly.

One typical component of disposable absorbent articles is core wraps. Acore wrap is typically a nonwoven material designed to contain thestorage layer and provide structural integrity when the storage layer iswet or dry. They may be a tissue wrap, or more typically they are anonwoven material which has been rendered hydrophilic.

A common method for rendering nonwoven fabrics hydrophilic is coatingthe surface of the nonwoven with hydrophilic surfactants. As thiscoating does not lead to a tight chemical bond between the nonwoven andthe surfactant, the surfactant can be washed off during use when theabsorbent article is wetted. The decrease in liquid strike-through timeis a desirable effect when the nonwoven is coated with surfactant.Liquid strike-through refers to liquid passing through the nonwovenfabric with liquid strike-through time referring to the time it takesfor a certain amount of liquid to pass through the nonwoven. However, asthe surfactant is washed off when coated nonwoven fabrics are exposed tothe liquid, the strike-through time in the next gushes is increased.This results in performance reduction during use on diapers or otherarticles comprising such nonwoven fabrics. Furthermore, at the same timeas liquid strike-through time decreases due to use of surfactants,surface tension of the liquid, which was in contact with the nonwovenfabric, is reduced. This reduction is undesirable, because it can causeincreased urine leakage in a diaper.

Another common method to render a nonwoven fabric hydrophilic is byapplying corona and/or plasma treatment. Plasma is an ionized form ofgas that can be obtained by ionizing a gas or liquid medium. Plasmas arewidely used for the treatment of organic and inorganic materials topromote adhesion between various materials. Polymers that havechemically inert surfaces with low surface energies do not allow goodcoatings with bondings and adhesives. Thus, these surfaces are treatedto make them receptive to bonding with other substrates, coatings,adhesives and printing inks.

However, corona and plasma treatments lead to low coating durabilityupon storage of the treated material, i.e., hydrophilicity decreasesover time.

Thus, there is a need for a hydrophilic coating of a nonwoven, which isdurable upon storage, is not easily washed off when wetted and allowsthe nonwoven to achieve fast liquid strike-through in multiple exposuresto liquid.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a disposable absorbentarticle comprising an absorbent core, the absorbent core comprising:

-   -   (a) a storage layer; and    -   (b) a durable hydrophilic fluid pervious core wrap, the core        wrap surrounding at least a portion of the storage layer, said        core wrap comprising:        -   (i) a core wrap substrate; and        -   (ii) a hydrophilicity boosting composition coated on the            substrate, the hydrophilicity boosting composition            comprising a hydrophilicity boosting amount of            nanoparticles, wherein the nanoparticles have a particle            size of from about 1 to about 750 nanometers.

A second aspect of the present invention provides a process for making adisposable absorbent article comprising an absorbent core, the absorbentcore comprising a storage layer and a durable hydrophilic core wrap, thecore wrap surrounding at least a portion of the storage layer and saidprocess comprising the step of:

-   -   coating a core wrap substrate with a hydrophilicity boosting        composition, the hydrophilicity boosting composition comprises a        hydrophilicity boosting amount of nanoparticles, wherein the        nanoparticles having a particle size of from about 1 to about        750 nanometers.

It should be understood that every limit given throughout thisspecification will include every lower or higher limit, as the case maybe, as if such lower or higher limit was expressly written herein. Everyrange given throughout this specification will include every narrowerrange that falls within such broader range, as if such narrower rangeswere all expressly written herein.

All documents cited are, in relevant part, incorporated herein byreference; the citation of any document is not to be construed as anadmission that it is prior art with respect to the present invention.All percentages, ratios and proportions are by weight, and alltemperatures are in degrees Celsius (° C.), unless otherwise specified.All measurements are in SI units, unless otherwise specified.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims which particularly pointout and distinctly claim the present invention, it is believed that thepresent invention will be better understood from the followingdescription of preferred embodiments, taken in conjunction with theaccompanying drawing wherein:

FIG. 1 is a partial cut-away top plan view of a disposable absorbentarticle including an absorbent core and a durable hydrophilic core wrap.

FIG. 2 is a partial sectional view along 2-2 of one alternativeembodiment of the absorbent core 10 of the disposable absorbent articleof FIG. 1.

FIG. 3 is a sectional view along 2-2 of another alternative embodimentof the absorbent core 10 of the disposable absorbent article of FIG. 1.

FIG. 4 is a sectional view along 2-2 of another alternative embodimentof the absorbent core 10 of the disposable absorbent article of FIG. 1.

FIG. 5 is a sectional view along 2-2 of another alternative embodimentof the absorbent core 10 of the disposable absorbent article of FIG. 1.

FIG. 6 is a sectional view along 2-2 of another alternative embodimentof the absorbent core 10 of the disposable absorbent article of FIG. 1.

FIG. 7 is a schematic side view of a process for forming an absorbentarticle according to the present invention.

FIG. 8 is a schematic top view of a strike-through plate which may beused to measure Liquid Strike-through of a substrate.

FIG. 9 is a sectional view along 9-9 of the strike-through plate of FIG.8.

FIG. 10 is a sectional perspective view along 10-10 of thestrike-through plate of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

The term “coating”, as used herein, includes coatings that completelycover a surface, or portion thereof (e.g., continuous coatings,including those that form films on the surface), as well as coatingsthat may only partially cover a surface, such as those coatings thatafter drying leave gaps in coverage on a surface (e.g., discontinuouscoatings). The later category of coatings may include, but is notlimited to, a network of covered and uncovered portions anddistributions of nanoparticles on a surface which may have spacesbetween the nanoparticles. In some embodiments, the coating preferablyforms at least one layer of nanoparticles on the surface which has beencoated, and is substantially uniform. However, when the coatingsdescribed herein are described as being applied to a surface, it isunderstood that the coatings need not be applied to, or that they coverthe entire surface. For instance, the coatings will be considered asbeing applied to a surface even if they are only applied to modify aportion of the surface.

The term “hydrophilic” describes fibers or surfaces of fibers, which arewettable by aqueous fluids (e.g., aqueous body fluids) deposited onthese fibers. Hydrophilicity and wettability are typically defined interms of contact angle and the strike-through time of the fluids, forexample through a nonwoven fabric. This is discussed in detail in theAmerican Chemical Society publication entitled “Contact Angle,Wettability and Adhesion”, edited by Robert F. Gould (Copyright 1964). Afiber or surface of a fiber is said to be wetted by a fluid (i.e.,hydrophilic) when either the contact angle between the fluid and thefiber, or its surface, is less than 90°, or when the fluid tends tospread spontaneously across the surface of the fiber, both conditionsare normally co-existing. Conversely, a fiber or surface of the fiber isconsidered to be hydrophobic if the contact angle is greater than 90°and the fluid does not spread spontaneously across the surface of thefiber.

As used herein, the term “hydrophilicity boosting” means a compositionwhen coated on a core wrap substrate to make a durable hydrophilic fluidpervious core wrap, produces a durable hydrophilic fluid pervious corewrap which has a liquid strike-through time for the first gush of lessthan or equal to about 6 seconds, more preferably less than or equal toabout 4 seconds, and has a liquid strike-through time for the fifth gushof test liquid, of preferably less than or equal to about 6 seconds,more preferably less than or equal to about 4 seconds, when tested inaccordance with the Strike-Through Test in the Test Methods section andfurther described herein.

As used herein, the term “comprising” means that the various components,ingredients, or steps can be conjointly employed in practicing thepresent invention. Accordingly, the term “comprising” is open-ended andencompasses the more restrictive terms “consisting essentially of” and“consisting of”.

The disposable absorbent articles of the present invention comprise anabsorbent core at least a portion of which is surrounded by a durablehydrophilic fluid pervious core wrap. Examples of illustrativedisposable absorbent articles, include but are not limited to, diapers,adult incontinence products, training pant, feminine hygiene pads, pantyliners and the like. The durable hydrophilic fluid pervious core wrapcomprises a core wrap substrate which has been coated with ahydrophilicity boosting composition. The substrate, and hydrophilicityboosting composition are both exemplified in more detail herein.

FIG. 1 is a plan view of a disposable absorbent article, specifically adiaper 20, which is a preferred embodiment of an absorbent articleaccording to the present invention. The diaper is shown in its flat out,uncontracted state (i.e., without elastic induced contraction). Portionsof the structure are cut away to show the underlying structure of thediaper 20, especially the absorbent core 10. The portion of the diaper20 that contacts a wearer is facing the viewer. The chassis 22 of thediaper 20 in FIG. 1 comprises the main body of the diaper 20. Thechassis 22 comprises an outer covering including a liquid pervioustopsheet 24 and/or a liquid impervious backsheet 26. The chassis mayalso include most or all of the absorbent core 10 encased between thetopsheet 24 and the backsheet 26.

For unitary absorbent articles, the chassis 22 comprises the mainstructure of the diaper with other features added to form the compositediaper structure. While the topsheet 24, the backsheet 26, and theabsorbent core 10 may be assembled in a variety of well-knownconfigurations, preferred diaper configurations are described generallyin U.S. Pat. No. 5,569,234 entitled “Disposable Pull-On Pant” issued toBuell et al. on Oct. 29, 1996; and U.S. Pat. No. 6,004,306 entitled“Absorbent Article With Multi-Directional Extensible Side Panels” issuedto Robles et al. on Dec. 21, 1999.

The topsheet 24 in FIG. 1 may be fully or partially elasticized or maybe foreshortened to provide a void space between the topsheet 24 and theabsorbent core 10. Exemplary structures including elasticized orforeshortened topsheets are described in more detail in U.S. Pat. No.5,037,416 entitled “Disposable Absorbent Article Having ElasticallyExtensible Topsheet” issued to Allen et al. on Aug. 6, 1991; and U.S.Pat. No. 5,269,775 entitled “Trisection Topsheets for DisposableAbsorbent Articles and Disposable Absorbent Articles Having SuchTrisection Topsheets” issued to Freeland et al. on Dec. 14, 1993.

The backsheet 26 in FIG. 1 is generally the portion of the diaper 20positioned with the absorbent core 10 between the backsheet 26 and thetopsheet 24. The backsheet 26 may be joined with the topsheet 24. Thebacksheet 26 prevents the exudates absorbed by the absorbent core 10 andcontained within the article 20 from soiling other external articlesthat may contact the diaper 20, such as bed sheets and undergarments. Inpreferred embodiments, the backsheet 26 is substantially impervious toliquids (e.g., urine) and comprises a laminate of a nonwoven and a thinplastic film such as a thermoplastic film having a thickness of about0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils). Suitable backsheetfilms include those manufactured by Tredegar Industries Inc. of TerreHaute, Ind. and sold under the trade names X15306, X10962, and X10964.Other suitable backsheet materials may include breathable materials thatpermit vapors to escape from the diaper 20 while still preventingexudates from passing through the backsheet 26. Exemplary breathablematerials may include materials such as woven webs, nonwoven webs,composite materials such as film-coated nonwoven webs, and microporousfilms such as manufactured by Mitsui Toatsu Co., of Japan under thedesignation ESPOIR NO and by EXXON Chemical Co., of Bay City, Tex.,under the designation EXXAIRE. Suitable breathable composite materialscomprising polymer blends are available from Clopay Corporation,Cincinnati, Ohio under the name HYTREL blend P18-3097.

Diapers 20 according to the present invention may be provided with are-closable fastening system (not shown) or may alternatively beprovided in the form of pant-type diapers.

The diaper 20 may also include such other features (not shown) as areknown in the art including front and rear ear panels, re-closablefastening system, lotion, waist cap features, pant type diapers,elastics and the like to provide better fit, containment and aestheticcharacteristics. Additional illustrative, but non-limiting, informationon construction, assembly, and the various components of disposablediapers may be found in U.S. Pat. No. 3,860,003 to Buell; U.S. Pat. No.5,151,092 to Buell; U.S. Pat. No. 5,221,274 to Buell; U.S. Pat. No.5,554,145 to Roe et al. on Sep. 10, 1996; U.S. Pat. No. 5,569,234 toBuell et al.; U.S. Pat. No. 5,580,411 to Nease et al.; U.S. Pat. No.6,004,306 to Robles et al.; U.S. Pat. No. 5,938,648 to LaVon et al.;U.S. Pat. No. 5,865,823 to Curro; U.S. Pat. No. 5,571,096 to Dobrin etal.; U.S. Pat. No. 5,518,801 to Chappell, et al.; U.S. Pat. No.4,573,986 to Minetola et al.; U.S. Pat. No. 3,929,135, to Thompson; U.S.Pat. No. 4,463,045 to Ahr, et al.; U.S. Pat. No. 4,609,518 to Curro etal.; U.S. Pat. No. 4,629,643 to Curro et al.; U.S. Pat. No. 5,037,416 toAllen et al.; U.S. Pat. No. 5,269,775 to Freeland et al.; U.S. Pat. No.4,610,678 to Weisman et al.; U.S. Pat. No. 4,673,402 to Weisman et al.;U.S. Pat. No. 4,888,231 to Angstadt; U.S. Pat. No. 5,342,338 to Roe;U.S. Pat. No. 5,260,345 to DesMarais et al.; U.S. Pat. No. 5,026,364 toRobertson; U.S. Pat. No. 3,848,594 to Buell; U.S. Pat. No. 4,846,815 toScripps; U.S. Pat. No. 4,946,527 to Battrell; U.S. Pat. No. 4,963,140 toRobertson et al.; U.S. Pat. No. 4,699,622 to Toussant et al.; U.S. Pat.No. 5,591,152 to Buell et al.; U.S. Pat. No. 4,938,753 to Van Gompel, etal.; U.S. Pat. No. 5,669,897 to LaVon, et al.; U.S. Pat. No. 4,808,178to Aziz et al.; U.S. Pat. No. 4,909,803 to Aziz et al.; U.S. Pat. No.4,695,278 to Lawson; U.S. Pat. No. 4,795,454 issued to Dragoo; U.S. Pat.No. 5,607,760 to Roe on; U.S. Pat. No. 5,609,587 to Roe; U.S. Pat. No.5,635,191 to Roe et al.; U.S. Pat. No. 5,643,588 to Roe et al.; and U.S.Pat. No. 5,968,025 to Roe et al.

The absorbent core 10 in FIG. 1 generally is disposed between thetopsheet 24 and the backsheet 26. The absorbent core 10 comprises adurable hydrophilic fluid pervious core wrap 42, (also referred toherein as durable hydrophilic core wrap, or core wrap) described in moredetail herein, and a storage layer 60 as shown in FIG. 2. The storagelayer 60 may comprise any absorbent material that is generallycompressible, conformable, non-irritating to the wearer's skin, andcapable of absorbing and retaining liquids such as urine and othercertain body exudates. The storage layer 60 may comprise a wide varietyof liquid-absorbent materials commonly used in disposable diapers andother absorbent articles such as comminuted wood pulp, which isgenerally referred to as air felt or fluff. Examples of other suitableabsorbent materials include creped cellulose wadding; melt blownpolymers, including co-form; chemically stiffened, modified orcross-linked cellulosic fibers; tissue, including tissue wraps andtissue laminates, absorbent foams, absorbent sponges, superabsorbentpolymers (such as superabsorbent fibers), absorbent gelling materials,or any other known absorbent material or combinations of materials.Examples of some combinations of suitable absorbent materials are fluffwith absorbent gelling materials and/or superabsorbent polymers, andabsorbent gelling materials and superabsorbent fibers etc. In oneoptional embodiment the storage layer is air felt free, that is, itcontains no air felt. The storage layer may further comprise minoramounts (typically less than 10%) of non-liquid absorbent materials,such as adhesives, waxes, oils and the like.

Exemplary absorbent structures for use as the absorbent assemblies aredescribed in U.S. Pat. No. 4,834,735, entitled “High Density AbsorbentMembers Having Lower Density and Lower Basis Weight Acquisition Zones”,issued to Alemany et al. on May 30, 1989; and U.S. Pat. No. 5,625,222entitled “Absorbent Foam Materials For Aqueous Fluids Made From highInternal Phase Emulsions Having Very High Water-To-Oil Ratios” issued toDesMarais et al. on Jul. 22, 1997.

FIG. 2 is a sectional view along 2-2 showing a section of onealternative embodiment of the absorbent core 10 of the diaper of FIG. 1.In FIG. 2 the storage layer 60 is wrapped by a core wrap 42 in a in aC-fold. The core wrap 42 comprises a substrate which has been coatedwith a hydrophilicity boosting composition which contains nanoparticles75. The substrate may be a nonwoven, a polymeric film or combinationsthereof. The substrate, hydrophilicity boosting composition, thenonwoven, and the porous polymeric film are all exemplified in moredetail herein.

The durable hydrophilic core wrap of the present invention provides asubstrate which has both an extended shelf life and wear life. Priorhigh-energy treatments tended to have a short shelf life. That is,during the time from purchase to ultimate use and disposal by theconsumer the substrate would trend to loose its hydrophilicity.Surfactant treatments, such as those of the prior art, on the other handwould often have an adequate shelf life, but have an inadequate wearlife. That is, upon contact with bodily fluids, such as urine, thesubstrate would instantly being to loose its hydrophilic properties.This may even lead to a surface which repels the bodily fluids it isdesigned to absorb even though the absorbent article has not reached itstotal absorbance capacity.

The hydrophilic core wrap of the present invention suffers neither ofthese limitations as the substrates treated with the hydrophilicityboosting composition of the present invention have a long shelf life andlong wear life, that is the hydrophilic properties of the core wrap arenot substantially lost over time or upon contact with bodily fluids suchas urine.

In one optional embodiment of the present invention the hydrophilic corewrap has a wash-off surface tension of greater than about 65 mN/m, whentested in accordance with the Determination of surface tension Test inthe Test Methods section and further described herein.

In one optional embodiment of the present invention the absorbent corecomprises, in addition to the storage layer and the durable hydrophiliccore wrap, an acquisition system, which comprises an upper acquisitionlayer facing towards the wearer and a lower acquisition layer. In onepreferred embodiment the upper acquisition layer comprises a nonwovenfabric whereas the lower acquisition layer preferably comprises amixture of chemically stiffened, twisted and curled fibers, high surfacearea fibers and thermoplastic binding fibers. In another preferredembodiment both acquisition layers are provided from a non-wovenmaterial, which is preferably hydrophilic. The acquisition layerpreferably is in direct contact with the storage layer. Furthermore, thestorage layer or parts thereof, such as the upper acquisition layer, mayoptionally be coated with the hydrophilicity boosting composition.

FIG. 3 is a sectional view along 2-2 showing a section of onealternative embodiment of the absorbent core 10 of the diaper of FIG. 1.In FIG. 3 the storage layer 60 is surrounded or enveloped by the corewrap 42. The core wrap 42 comprises a substrate which has been coatedwith a hydrophilicity boosting composition, both of which areexemplified in more detail herein.

FIG. 4 is a sectional view along 2-2 showing a section of onealternative embodiment of the absorbent core 10 of the diaper of FIG. 1.In FIG. 3 the storage layer 60 is surrounded or enveloped by the corewrap 42. The core wrap 42 comprises a fluid receiving top layer 70 and abottom layer 80. The fluid receiving top layer 70 and the bottom layer80 can be same or different. That is they may be the same substratecoated with the same hydrophilicity boosting composition, the differentsubstrates coated with the same hydrophilicity boosting composition ordifferent substrates coated with different hydrophilicity boostingcomposition, etc.

In one optional embodiment of the present invention the top layer 70 andthe bottom layer 80 may comprise non-woven material. One preferredmaterial is a so-called SMS material, comprising a spunbonded, amelt-blown and a further spunbonded layers. The top layer 70 and thebottom layer 80 may be provided from two or more separate sheets ofnonwoven materials or they may be alternatively provided from a unitarysheet of material. SMS materials are exemplified in more detail herein.

In one alternative embodiment of the present invention only a portion ofthe substrate is coated with the hydrophilicity boosting composition.This is optional embodiment is illustrated in FIGS. 5 and 6. FIG. 5 is asectional view along 2-2 showing a section of the absorbent core 10 ofthe diaper of FIG. 1. In FIG. 5 the storage layer 60 is wrapped by acore wrap 42 in a in a C-fold. The core wrap 42 comprises two portions:a portion which has been coated with the hydrophilicity boostingcomposition, or coated portion 90, and a portion which is not coatedwith the hydrophilicity boosting composition, or uncoated portion 30.

An alternative embodiment to that illustrated in FIG. 5 may be found inFIG. 6. FIG. 6 is a sectional view along 2-2 showing a section of onealternative embodiment of the absorbent core 10 of the diaper of FIG. 1.In FIG. 6 the storage layer 60 is surrounded or enveloped the core wrap42. The core wrap 42 comprises a top layer 70, which has been coatedwith the hydrophilicity boosting composition, and forms a coated portion90; and a bottom layer 80 which is not coated with the hydrophilicityboosting composition, and forms an uncoated portion 30.

In another alternative embodiment the uncoated portion 30 may beoptionally coated with a different composition to give it differentphysical properties the coated portion 90. For example, the uncoatedportion 30 may be coated with a composition to make it more hydrophobic,or it is coated with a hydrophilicity boosting composition different tothat used to coat the coated portion 90.

The durable hydrophilic core wrap of the present invention willpreferably have a basis weight of between about 1 grams per square meter(or gsm) and about 100 gsm, more preferably between about 2 gsm andabout 50 gsm, even more preferably between about 5 gsm and about 30 gsm.

Core Wrap Substrate—The durable hydrophilic core wrap of the presentinvention comprises a core wrap substrate (substrate) which has beencoated with a hydrophilicity boosting composition. The substrate ofinterest herein may comprise any known type of substrate, including butnot limited to fabrics, garments, textiles, and films. In certainembodiments, the substrate may comprise one or more fibers. A fiber isdefined as a fine hairlike structure, of animal, vegetable, mineral, orsynthetic origin. Commercially available fibers have diameters rangingfrom less than about 0.001 mm (about 0.00004 in) to more than about 0.2mm (about 0.008 in) and they come in several different forms: shortfibers (known as staple, or chopped), continuous single fibers(filaments or monofilaments), untwisted bundles of continuous filaments(tow), and twisted bundles of continuous filaments (yarn).

The substrate may comprise fibers made by nature (natural fibers), madeby man (synthetic or man-made), or combinations thereof. Example naturalfibers include but are not limited to: animal fibers such as wool, silk,fur, and hair; vegetable fibers such as cellulose, cotton, flax, linen,and hemp; and certain naturally occurring mineral fibers. Syntheticfibers can be derived from natural fibers or not. For example syntheticfibers which are derived from natural fibers, include but are notlimited to, rayon and lyocell, both of which are derived from cellulose.Synthetic fibers which are not derived from natural fibers can bederived from other natural sources or from mineral sources. Exemplarysynthetic fibers derived from natural sources, include but are notlimited to, polysaccharides such as starch. Exemplary fibers frommineral sources, include but are not limited to, polyolefin fibers suchas polypropylene and polyethylene fibers, which are derived frompetroleum, and silicate fibers such as glass and asbestos. Syntheticfibers are commonly formed, when possible, by fluid handling processes(e.g., extruding, drawing, or spinning a fluid such as a resin or asolution). Synthetic fibers are also formed by solid handling sizereduction processes (e.g., mechanical chopping or cutting of a largerobject such as a monolith, a film, or a fabric).

Examples of suitable synthetic fibers which may comprise all or part ofthe core wrap substrates of the present invention include but are notlimited, to nylon (polyamide), acrylic (polyacrylonitrile), aramid(aromatic polyamide), polyolefin (polyethylene and polypropylene),polyester, butadiene-styrene block copolymers, natural rubber, latex,spandex (polyurethane) and combinations thereof.

Synthetic fibers that contain more than one type of repeat unit canresult from combining repeat units at the molecular level within eachmacromolecular strand (co-polymer), between macromolecular strands(homopolymer blends), or combinations thereof (co-polymer blends); orthey can result from combining repeat units at a higher scale level withdistinct nanoscopic, microscopic, or macroscopic phases (e.g.,multicomponent fibers). Each component of a multicomponent fiber cancomprise a homopolymer, a co-polymer, or blends thereof. Bicomponentfibers are common versions of multicomponent fibers. The two or moretypes of repeat units in a copolymer can be arranged randomly or inalternating blocks of each type. Blocks of different types of repeatunits can joined to one another at their respective ends (blockco-polymers) or between the respective end of at least one block (graftco-polymers).

Nonwoven materials are a type of fabric typically made from fibers in aweb format. Nonwoven materials are described by Butler I, Batra S K, etal, Nonwovens Fabrics Handbook, Association of the Nonwoven FabricsIndustry, 1999, and by Vaughn E A, Nonwoven Fabric Sampler andTechnology Reference, Association of the Nonwoven Fabrics Industry.

Substrates comprising nonwoven materials can be formed by directextrusion processes during which the fibers and the nonwoven materialsare formed at about the same point in time, or by preformed fibers whichcan be laid into nonwoven materials at a distinctly subsequent point intime. Exemplary direct extrusion processes include but are not limitedto: spunbonding, meltblowing, solvent spinning, electrospinning, andcombinations thereof typically forming layers. Exemplary “laying”processes include wetlaying and drylaying. Example drylaying processesinclude but are not limited to airlaying, carding, and combinationsthereof typically forming layers. Combinations of the above processesyield nonwovens commonly called hybrids or composites. Exemplarycombinations include but are not limited to spunbond-meltblown-spunbond(SMS), spunbond-carded (SC), spunbond-airlaid (SA), meltblown-airlaid(MA), and combinations thereof, typically in layers. Combinations whichinclude direct extrusion can be combined at the about the same point intime as the direct extrusion process (e.g., spinform and coform for SAand MA), or at a subsequent point in time. In the above examples, one ormore individual layers can be created by each process. For instance, SMScan mean a three layer, ‘sms’ nonwoven materials, a five layer ‘ssmms'nonwoven materials, or any reasonable variation thereof wherein thelower case letters designate individual layers and the upper caseletters designate the compilation of similar, adjacent layers.

The fibers in nonwoven materials are typically joined to one or moreadjacent fibers at some of the overlapping junctions. This includesjoining fibers within each layer and joining fibers between layers whenthere is more than one layer. Fibers can be joined by mechanicalentanglement, by chemical bond or by combinations thereof.

Fibers and nonwoven materials can be subjected to additional treatmentafter formation. For nonwoven materials, additional treatment commonlyoccurs after the fibers are joined to one another (post-treatment).Examples of additional treatments include but are not limited tomechanical stresses, chemical additives, or combinations thereof.

It is also within the scope of the present invention that the term “corewrap substrate” includes laminates of two or more substrates or webs.Commercially available laminates, or purpose built ones would also bewithin the scope of the present invention. Additionally, the substratesmay be flat or textured. The formation of textured substrates andlaminates forms no part of this invention. The following discussion isfor convenience of formulation, but is not intended to limit the type ofsubstrate used herein.

In one optional embodiment of the present invention the substrate istreated with a high-energy surface treatment. This high-energy treatmentmay be prior to or concurrent with the coating of the substrate with thehydrophilicity boosting composition. The high-energy treatment may beany suitable high-energy treatment for increasing the hydrophilicity ofa substrate. Suitable high-energy treatments, include but are notlimited to, corona discharge treatment, plasma treatment, UV radiation,ion beam treatment, electron beam treatment and combinations thereof.

High-energy surface treatments which increase surface energy are usefulin that in combination with the nanoparticles they can provide thesurface with durable hydrophilic properties. In turn, increased surfaceenergy increases the wettability of the substrate without use ofsurfactants in the dispersion to achieve wetting. Avoiding use ofsurfactant is useful for reasons previously discussed. In a non-limitingexample, corona treatment places transient charges on fibrousthermoplastic surfaces. As discussed earlier, partial or full chargesdissipate over time, and maintaining partial or full charges on fibrousthermoplastic surfaces is a common limitation. However, it has beenfound that corona treatment in combination with the nanoparticles can beused to place a durable charge on the material so that water continuesto be attracted to the material after time elapses. The use ofnanoparticles in conjunction with high-energy surface treatments, canconvert the transient properties of such treatments to more durableproperties. In a non-limiting example, corona treatment of a 13 gram persquare meter hydrophobic SMS polypropylene nonwoven subsequently treatedwith a hydrophilicity boosting compositions and dried exhibitedconsistently fast strikethrough following multiple gushes or insults.Without wishing to be bound by theory, the corona treatment increasedthe surface energy for the fiber. The hydrophilicity boostingcompositions without a surfactant was brought into contact with thefiber surfaces before the charges could dissipate. The higher surfaceenergy enabled the dispersion to wet the fibrous surfaces better thanwould have been possible without the corona treatment. On the surfaceswhich are wetted, the nanoparticles associate with the partial or fullcharge on the surface which would otherwise be transient. Thisassociation may take the form of a van der Waals interaction or the formof some other interaction or bond. The nanoparticles are sufficientlysmall to render the associations sufficient strong to withstand multiplestrikethroughs. The nanoparticle is sufficiently large to resistrotation away from oxygen into the polymer or dissipate in general.

Additional illustrative, but non limiting, information on mechanicalentanglement and by chemical bonding of fiber, as well as additionaltreatments to nonwoven material, such as high-energy treatment, may befound in copending U.S. Published Patent Application No. 2002/0151634(application Ser. No. 10/060,708) filed on Jan. 30, 2002, published onOct. 17, 2002, P&G Docket No. 8408M; U.S. Published Patent ApplicationNo. 2002/0192366 (application Ser. No. 10/060,694) filed on Jan. 30,2002, published on Dec. 19, 2002, P&G Docket No. 8837Q; U.S. PublishedPatent Application No. 2002/0150678 (application Ser. No. 10/060582)filed on Jan. 30, 2002, published on Oct. 17, 2002, P&G Docket No.8838Q; U.S. patent application Ser. No. 10/338,603 filed on Jan. 8,2003, P&G Docket No. 8857; and U.S. patent application Ser. No.10/338,610 filed on Jan. 8, 2003, P&G Docket No. 8858.

The following patents may referred to for their disclosures related tothe substrate: U.S. Pat. No. 3,862,472 issued Jan. 28, 1975; U.S. Pat.No. 3,982,302 issued Sep. 28, 1976; U.S. Pat. No. 4,004,323 issued Jan.25, 1977; U.S. Pat. No. 4,057,669 issued Nov. 8, 1977; U.S. Pat. No.4,097,965 issued Jul. 4, 1978; U.S. Pat. No. 4,176,427 issued Dec. 4,1979; U.S. Pat. No. 4,130,915 issued Dec. 26, 1978; U.S. Pat. No.4,135,024 issued Jan. 16, 1979; U.S. Pat. No. 4,189,896 issued Feb. 26,1980; U.S. Pat. No. 4,207,367 issued Jun. 10, 1980; U.S. Pat. No.4,296,161 issued Oct. 20, 1981; U.S. Pat. No. 4,309,469 issued Jan. 25,1982; U.S. Pat. No. 4,682,942 issued Jul. 28, 1987; and U.S. Pat. Nos.4,637,859; 5,223,096; 5,240,562; 5,556,509; and 5,580,423.

Hydrophilicity Boosting Composition—The hydrophilicity boostingcompositions of the present invention comprise a hydrophilicity boostingamount of nanoparticles. By hydrophilicity boosting amount, it isintended that an amount of nanoparticles be present in thehydrophilicity boosting compositions which are sufficient to make asubstrate to which it is applied more hydrophilic. Such amounts arereadily ascertained by one of ordinary skill in the art and are based onmany factors, including but not limited to, the substrate used, thenanoparticles used, the desired hydrophilicity of the durablehydrophilic core wrap, the consumer product in which the absorbent coreis used, etc. Preferably the nanoparticles are present in thehydrophilicity boosting compositions at levels of from about 0.0001% toabout 20%, preferably from about 0.001% to about 15 %, and morepreferably from about 0.001% to about 10%, by weight of the composition.

Typically the amount of hydrophilicity boosting compositions present ona core wrap substrate will vary depending upon many factors, includingbut not limited to, the substrate used, the nanoparticles used, thedesired hydrophilicity of the durable hydrophilic core wrap, theconsumer product in which the absorbent core is used, etc. Preferably,the amount of hydrophilicity boosting compositions on the core wrapsubstrate will be present invention will be between about 0.01 grams ofhydrophilicity boosting composition per square meter of substrate (orgsm substrate) and about 30 gsm substrate, more preferably between about0.01 gsm substrate and about 20 gsm substrate, even more preferablybetween about 0.1 gsm substrate and about 10 gsm substrate. In onepreferred embodiment of the present invention the nanoparticles areapplied to the substrate as a dispersion in a carrier.

Nanoparticles are particles which have a particle size, that isdiameter, which is of the order of magnitude of nanometers. That is,nanoparticles have a particle size ranging from about 1 to about 750nanometers. Such particles are technologically significant since theyare utilized to produce durable hydrophilic core wraps that have noveland useful properties due to the very small dimensions of theirparticulate constituents. Nanoparticles with particle sizes ranging fromabout 2 nm to about 750 nm can be economically produced. Non-limitingexamples of particle size distributions of the nanoparticles are thosethat fall within the range from about 2 nm to less than about 750 nm,alternatively from about 2 nm to less than about 200 nm, andalternatively from about 2 nm to less than about 150 nm.

The particle size of the nanoparticles is the largest diameter of ananoparticle.

The mean particle size of various types of nanoparticles may differ fromthe particle size distribution of the nanoparticles particles. Forexample, a layered synthetic silicate can have a mean particle size ofabout 25 nanometers while its particle size distribution can generallyvary between about 10 nm to about 40 nm. (It should be understood thatthe particle sizes that are described herein are for particles when theyare dispersed in an aqueous medium and the mean particle size is basedon the mean of the particle number distribution. Non-limiting examplesof nanoparticles can include crystalline or amorphous particles with aparticle size from about 2 to about 750 nanometers. Boehmite alumina canhave an average particle size distribution from 2 to 750 nm.)

When the hydrophilicity boosting composition is present on the substrateit will typically be a substantially uniform coating. When thehydrophilicity boosting composition dries, for example any waterevaporates, the nanoparticles may aggregate together on the substrateforming larger particles, or even appear film like, depending upon theobservation method used. In any event, the application of ahydrophilicity boosting composition comprising nanoparticles, providesfor a uniform coat of the substrate.

Either organic or inorganic nanoparticles may be used in thehydrophilicity boosting composition of the present invention. Suitableorganic nanoparticle include, but are not limited to, nanolatexes. A“nanolatex”, as used herein, is a latex with particle sizes less than orequal to about 750 nm. A “latex” is a colloidal dispersion ofwater-insoluble polymer particles that are usually spherical in shape.Nanolatexes may be formed by emulsion polymerization. “Emulsionpolymerization” is a process in which monomers of the latex aredispersed in water using a surfactant to form a stable emulsion followedby polymerization. Particles are produced with can range in size fromabout 2 to about 600 nm.

While organic nanoparticles are within the scope of the presentinvention, inorganic nanoparticles are preferred. Inorganicnanoparticles generally exist as oxides, silicates, carbonates andhydroxides. Some layered clay minerals and inorganic metal oxides can beexamples of nanoparticles. The layered clay minerals suitable for use inthe present invention include those in the geological classes of thesmectites, the kaolins, the illites, the chlorites, the attapulgites andthe mixed layer clays. Typical examples of specific clays belonging tothese classes are the smectices, kaolins, illites, chlorites,attapulgites and mixed layer clays. Smectites, for example, includemontmorillonite, bentonite, pyrophyllite, hectorite, saponite,sauconite, nontronite, talc, beidellite, volchonskoite and vermiculite.Kaolins include kaolinite, dickite, nacrite, antigorite, anauxite,halloysite, indellite and chrysotile. Illites include bravaisite,muscovite, paragonite, phlogopite and biotite. Chlorites includecorrensite, penninite, donbassite, sudoite, pennine and clinochlore.Attapulgites include sepiolite and polygorskyte. Mixed layer claysinclude allevardite and vermiculitebiotite. Variants and isomorphicsubstitutions of these layered clay minerals offer unique applications.

Layered clay minerals may be either naturally occurring or synthetic. Anexample of one non-limiting embodiment of the coating composition usesnatural or synthetic hectorites, montmorillonites and bentonites.Another embodiment uses the hectorites clays commercially available, andtypical sources of commercial hectorites are the LAPONITEs™ fromSouthern Clay Products, Inc., U.S.A.; Veegum Pro and Veegum F from R. T.Vanderbilt, U.S.A.; and the Barasyms, Macaloids and Propaloids fromBaroid Division, National Read Comp., U.S.A.

In one preferred embodiment of the present invention the nanoparticlescomprise a synthetic hectorite a lithium magnesium silicate. One suchsuitable lithium magnesium silicate is LAPONITE™, which has the formula:[Mg_(w)Li_(x)Si₈O₂₀OH_(4-y)F_(y)]^(z−)wherein w=3 to 6, x=0 to 3, y=0 to 4, z=12 −2w−x, and the overallnegative lattice charge is balanced by counter-ions; and wherein thecounter-ions are selected from the group consisting of selected Na⁺, K⁺,NH₄ ⁺, Cs⁺, Li⁺, Mg⁺⁺, Ca⁺⁺, Ba⁺⁺, N(CH₃)₄ ⁺ and mixtures thereof. (Ifthe LAPONITE™ is “modified” with a cationic organic compound, then the“counter-ion” could be viewed as being any cationic organic group (R).)

Other suitable synthetic hectorites include, but are not limited toisomorphous substitutions of LAPONITE™, such as, LAPONITE B™, LAPONITES™, LAPONITE XLS™, LAPONITE RD™, LAPONITE XLG™, and LAPONITE RDS™.

The nanoparticles may also be other inorganic materials, includinginorganic oxides such as, but not limited to, titanium oxide silica,zirconium oxide, aluminum oxide, magnesium oxide and combinationsthereof. Other suitable inorganic oxides include various inorganicoxides of alumina and silica.

In one preferred embodiment of the present invention the nanoparticlescomprise a Boehmite alumina ([Al(O)(OH)]_(n)) which is a waterdispersible, inorganic metal oxide that can be prepared to have avariety of particle sizes or range of particle sizes, including a meanparticle size distribution from about 2 nm to less than or equal toabout 750 nm. For example, a boehmite alumina nanoparticle with a meanparticle size distribution of around 25 nm under the trade name DisperalP2™ and a nanoparticle with a mean particle size distribution of around140 nm under the trade name of Dispal® 14N4-25 are available from NorthAmerican Sasol, Inc.

Use of mixtures of nanoparticles in the hydrophilicity boostingcompositions is also within the scope of the present invention.

In one preferred embodiment of the present invention the nanoparticlesare selected from the group consisting of titanium dioxide, Boehmitealumina, sodium magnesium lithium fluorosilicates and combinationsthereof.

Optional ingredients—The hydrophilicity boosting compositions of thepresent invention may also include optional ingredients such as, acarrier, surfactant and adjunct ingredients.

Optional ingredients, when present, are typically employed incompositions at levels of from about 0.001% to about 99.9%, preferablyfrom about 0.01% to about 98%, and more preferably from about 0.1% toabout 96%, by weight of the composition.

Suitable carriers include liquids, solids and gases. One preferredcarrier is water, which can be distilled, deionized, or tap water. Wateris valuable due to its low cost, availability, safety, andcompatibility.

Optionally, in addition to or in place of water, the carrier cancomprise a low molecular weight organic solvent. Preferably, the solventis highly soluble in water, e.g., ethanol, methanol, acetone, ethyleneglycol, propanol, isopropanol, and the like, and mixtures thereof. Lowmolecular weight alcohols can reduce the surface tension of thenanoparticle dispersion to improve wettability of the substrate. This isparticularly helpful when the substrate is hydrophobic. Low molecularweight alcohols can also help the treated substrate to dry faster. Theoptional water soluble low molecular weight solvent can be used at anysuitable level. The carrier can comprise any suitable amount of thecomposition, including but not limited to from about 10% to about 99%,alternatively from about 30% to about 95%, by weight of the coatingcomposition.

Surfactants are an optional ingredient in some embodiments of thepresent invention. Surfactants are especially useful in the coatingcomposition as wetting agents to facilitate the dispersion ofnanoparticles onto the substrate. Surfactants are preferably includedwhen the coating composition is used to treat a hydrophobic substrate.

Suitable surfactants can be selected from the group including anionicsurfactants, cationic surfactants, nonionic surfactants, amphotericsurfactants, ampholytic surfactants, zwitterionic surfactants andmixtures thereof. Nonlimiting examples of surfactants useful in thecompositions of the present invention are disclosed in McCutcheon's,Detergents and Emulsifiers, North American edition (1986), published byAllured Publishing Corporation; McCutcheon's, Functional Materials,North American Edition (1992); U.S. Pat. Nos. 5,707,950 and 5,576,282;and U.S. Pat. No. 3,929,678, to Laughlin et al., issued Dec. 30, 1975.

When a surfactant is used in the coating composition, it may be added atan effective amount to provide facilitate application of the coatingcomposition. Surfactant, when present, is typically employed incompositions at levels of from about 0.0001% to about 60%, preferablyfrom about 0.001% to about 35%, and more preferably from about 0.001% toabout 25%, by weight of the composition.

Nonlimiting examples of surfactants, including preferred nonionicsurfactants, useful herein typically at levels from about 0.001% toabout 60%, by weight, include nonionic and amphoteric surfactants suchas the C₁₂-C₁₈ alkyl ethoxylates (“AE”) including the so-called narrowpeaked alkyl ethoxylates and C₆-C₁₂ alkyl phenol alkoxylates (especiallyethoxylates and mixed ethoxy/propoxy), C₁₂-C₁₈ betaines andsulfobetaines (“sultaines”), C₁₀-C₁₈ amine oxides, and the like.

Another class of useful surfactants is silicone surfactants and/orsilicones. They can be used alone and/or alternatively in combinationwith the alkyl ethoxylate surfactants described herein. Nonlimitingexamples of silicone surfactants are the polyalkylene oxidepolysiloxanes having a dimethyl polysiloxane hydrophobic moiety and oneor more hydrophilic polyalkylene side chains, and having the generalformula:R¹—(CH₃)₂SiO—[(CH₃)₂SiO]_(a)—[(CH₃)(R¹)SiO]_(b)—Si(CH₃)₂—R¹wherein a+b are from about 1 to about 50, and each R¹ is the same ordifferent and is selected from the group consisting of methyl and apoly(ethyleneoxide/propyleneoxide) copolymer group having the generalformula: —(CH₂)_(n)O(C₂H₄O)_(c)(C₃H₆O)_(d)R², wherein n is 3 or 4; totalc (for all polyalkyleneoxy side groups) has a value of from 1 to about100, alternatively from about 6 to about 100; total d is from 0 to about14; alternatively d is 0; total c+d has a value of from about 5 to about150, alternatively from about 9 to about 100 and each R² is the same ordifferent and is selected from the group consisting of hydrogen, analkyl having 1 to 4 carbon atoms, and an acetyl group, alternativelyhydrogen and methyl group. Each polyalkylene oxide polysiloxane has atleast one R¹ group being a poly(ethyleneoxide/propyleneoxide) copolymergroup. Silicone superwetting agents are available from Dow Corning assilicone glycol copolymers (e.g., Q2-5211 and Q2-5212).

It is also within the scope of the present invention to use a mixture ofsurfactants.

Adjunct ingredients—The compositions can contain other optional adjunctingredients, including but not limited to process aids, antimicrobialpreservatives, antioxidants, anti-static agents, chelating agents,colorants, dyes, filler salts, fungicides, insect and moth repellantagents, germicides, hydrotropes, metallic salts. These optionalingredients may be included at any desired level, but are typicallyadded at a level of from about 0.0001% to about 99.99% by weight of thecomposition.

Applying the hydrophilicity boosting composition to the substrate—Thehydrophilicity boosting composition can be applied to the substrate inany suitable manner. The hydrophilicity boosting composition can beapplied to the substrate when the substrate is at least partiallyimmersed in a bath of the composition (immersive processes), or withoutimmersing the substrate in the coating composition (non-immersiveprocesses).

In one embodiment of the present invention the hydrophilicity boostingcomposition is applied by kiss-roll coating. In kiss-roll coating, thecomposition is kept in a suitable bath. A rotating cylinder or any otherdevice suitable for this process, is contacting the composition with atleast a part of its surface. Thus, the composition is spread on thesurface of the cylinder. The substrate is brought into contact with thecylinder while the cylinder already has the composition spread on itssurface. In this process, the amount of composition applied on thesubstrate can be controlled easily and it is possible to avoid soakingthe substrate with composition.

Alternatively to the kiss-roll coating, the composition can also besprayed on the surface of the plurality of fibers. Like the kiss-rollcoating, spraying enables low and easily controllable add-on level ofaqueous solution, which is preferred in the present invention. Otheralternative methods include, but are not limited to, printing such as,rotary, gravure, flexographic printing, ink jet printing, slot coatingand the like.

Process for Making a Disposable Absorbent Article—FIG. 7 illustrates oneoptional embodiment of manufacturing a disposable absorbent article,more specifically the step of producing an absorbent core. Fromdispensing roller 110 a durable hydrophilic core wrap 42 is dispensedonto a conveyer belt 120. The durable hydrophilic core wrap 42 waspreviously formed by coating a substrate with a hydrophilicity boostingcomposition. The durable hydrophilic core wrap 42 moves along theconveyer belt 120 to a point 130 where the components of the storagelayer 60 are dispensed from bins 140 and 150. Air felt 160 dispensedfrom bin 150 mixes with absorbent gelling material 170 prior todeposition on the hydrophilic core wrap 42 at point 130.

At stage 170 a portion of the storage layer 60 is surrounded by thedurable hydrophilic core wrap 42. Examples surrounding the storage layer60, such as encapsulating or enveloping, this may be found describedherein with reference to FIGS. 2 to 6 inclusive. Lastly, at stage 180the ends of the durable hydrophilic core wrap 42 are sealed. Suitablemethods of sealing include, but are not limited to, adhesive, heat,ultrasonic and combinations thereof. The formed absorbent core may thenbe further processed to incorporate it into a disposable absorbentarticle, such as in between the topsheet and backsheet of a disposablediaper.

EXAMPLES

Hydrophilicity boosting compositions, according to the presentinvention, are prepared as follows: % Wt of Component Component 1 2 3 45 6 7 8 9 10 11 12 13 Nanoparticle¹ 0.1 0.05 0.05 0.1 1 Nanoparticle²0.1 0.05 0.05 0.1 Nanoparticle³ 1 1 4 Nanoparticle⁴ 1 Surfactant⁵ 0.0750.075 0.075 0.075 0.075 0.075 Surfactant⁶ 0.025 0.025 Water quantitysufficient to 100%¹LAPONITE B ™ is sodium magnesium lithium fluorosilicate from SouthernClay Products, Inc.²LAPONITE RD ™ is sodium magnesium lithium silicate from Southern ClayProducts, Inc.³Disperal 14N4-25 is a boehmite alumina nanoparticle available fromNorth American Sasol, Inc⁴ZSM5 is a nanosized zeolite with a particle size from 70 to about 400nm.⁵Neodol 91-6⁶Silwet L-77

Test Methods—Unless otherwise stated, all tests are performed understandard laboratory conditions (50% humidity and at 73° F. (23° C.)).

Contact Angle—Dynamic contact angles are measured using the FTA200Dynamic Contact Angle Analyzer, made by First Ten Angstroms, USA. Asingle drop of test solution is dispensed onto the sample substrate. Adigital video recording is made while the drop spreads out across thesurface of the substrate and the FTA200 software measures the contactangle of the liquid with the substrate as a function of time.

Determination of surface tension—The surface tension (unit: mN/m) isdetermined according to the following test. Apparatus: Equipment: K10tensiometer provided by Krüss GmbH, Germany or equivalent. The vesselelevation speed should be 4 mm/min. Liquid surface height should besensed automatically when using a plate or a ring. The equipment must beable to adjust the sample position automatically to the correct height.Precision of test should be ±0.1 mN/m.

Procedure (i) Calibration: Pour 40 ml of saline (0.9 wt % NaCl indeionized water) into a cleaned beaker. Test the surface tension of thesaline with a platinum ring or a platinum plate using the methoddescribed in equipment instructions. The surface tension should be 71-72mN/m at 20° C. (ii) Method: Clean the beaker with deionized water andisopropanol, including burning it out with a gas burner for a fewseconds. Wait until the beaker temperature equilibrates to roomtemperature is reached. Place ten 60×60 mm pieces of test nonwoven intoa cleaned beaker. The nonwoven should have a basis weight of at least 10grams per square meter (or gsm). Add 40 ml of saline (0.9 wt % NaCl indeionized water) and stir by hand with a clean surfactant-free plasticstick for 10 seconds. Let the solution with nonwoven stand for 5minutes. Stir again by hand for ten seconds. Remove the nonwovens fromthe saline with a clean surfactant-free plastic stick. Let the solutionstand for ten minutes. Then test the liquids surface tension with aplatinum plate or platinum ring; using the method described in theequipment instructions. The measured surface tension is the wash-offsurface tension.

Liquid Strike-Through Test—The liquid strike-through time is measuredusing Lister-type strike-through equipment, manufactured by Lenzing AG,Austria. Test procedure is based on standardized EDANA (EuropeanDisposables And Nonwovens Association) method 150.3-96, with the testsample placed on an absorbent pad comprised of ten plies of filter paper(Ahlstrom Grade 632 obtained from Empirical Manufacturing Co., Inc., orequivalent). In a typical experiment, three consecutive 5ml gushes oftest liquid (0.9% saline solution) are applied to a nonwoven sample atone minute intervals and the respective strike-through times arerecorded without changing the absorbent pad.

In addition to measuring the strike-through time for the first gush, asdescribed in the Edana Method, the test described below does not onlymeasure the first gush but several subsequent gushes, especially thefifth gush.

Apparatus—Lister Strike-through Equipment-(i) A Funnel fitted withmagnetic valve: Rate of discharge of 25 ml in 3.5 (+0.25) seconds; (ii)A Strike-through plate: Constructed of 25 mm thick acrylic glass. Thetotal weight of the plate must be 500 g. The electrodes should be ofnon-corrosive material. The electrodes are set in (4.0 mm×7.0 mm) crosssection grooves, cut in the base of the plate and fixed with quicksetting epoxy resin. FIGS. 8 9, and 10 illustrate a Strike-through plate200 containing electrodes 210. FIG. 8 is a top view of a Strike-throughplate 200, where as FIG. 9 is a sectional view along 9-9 of theStrike-through plate 200 of FIG. 8. FIG. 10 is a sectional perspectiveview along 10-10 of the Strike-through plate 200 of FIG. 8; (iii) Baseplate: A square of acrylic glass 125 mm×125 mm approximately; (iv) Ringstand to support the funnel; (v) Electronic Timer measuring to 0.01seconds; (vi) Burette with 50 ml capacity; and (vii) Core filter paperAhlström Grade 989 or equivalent (average Strike-through time 1.7 s+−0.3s, dimensions: 10×10 cm).

Procedure: (1) Carefully cut the required number of samples, 12.5cm×12.5 cm with touching the sample only at the edge of the sample. (2)Taking 10 plies of Core filter paper place one sample on the set of 10plies of filter paper on the base plate. The sample should be positionedon the filter paper in such a way that the side of the nonwoven, whichis intended to face the user's skin (when applied in an absorbentarticle) is uppermost. (3) Place the strike-through plate on top withthe center of the plate over the center of the test piece. Center theburette and the funnel over the plate. (4) Ensuring that the electrodesare connected to the timer, switch on the timer and set the clock tozero. (5) Fill the burette with saline solution (0.9 wt % NaCl indeionized water). (6) Keep the discharge valve of the funnel closed andrun 5.0 ml of liquid (=one gush) from the burette into the funnel. (7)Open the magnetic valve of the funnel to discharge 5.0 ml of liquid. Theinitial flow of liquid will complete the electrical circuit and startthe timer. It will stop when the liquid has penetrated into the pad andfallen below the level of the electrodes in the strike-through plate.(8) Record the time indicated on the electronic timer. (9) Wait 60seconds and repeat steps (4), and (6) to (9) for the second, the thirdgush and any subsequent gush, with each gush comprising 5 ml of liquid.(e.g., 5 ml into funnel, open magnetic valve, etc.) Record the Time forthe 1^(st), 2^(nd) and any subsequent gush in seconds.

Strike-through results for SMS polypropylene nonwoven materials (13grams per square meter) exposed to a Laboratory Corona Treater (Model#BD-20AC, manufactured by Electro-Technic Products Inc., USA) andcoating compositions according to the present invention are reported inTable 2. TABLE 2 Strike-through Times Strike-through Time (seconds)Sample 1st Gush 2^(nd) Gush 5th Gush 0.2% Laponite RD (Southern 2.5 2.83.0 Clay Products) 0.1% Disperal P2 (Condea) 2.4 2.6 2.1

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A disposable absorbent article comprising an absorbent core, saidabsorbent core comprising: (a) a storage layer; and (b) a durable,hydrophilic fluid pervious core wrap, said core wrap surrounding atleast a portion of said storage layer said core wrap comprising: (i) acore wrap substrate; and (ii) a hydrophilicity boosting compositioncoated on said substrate, said hydrophilicity boosting compositioncomprising a hydrophilicity boosting amount of nanoparticles, whereinsaid nanoparticles have a particle size of from about 1 to about 750nanometers.
 2. A disposable absorbent article according to claim 1wherein said substrate is selected from the group consisting of porouspolymeric films, nonwoven materials and combinations thereof.
 3. Adisposable absorbent article according to claim 2 wherein said nonwovenmaterial comprises fibers selected from the group consisting ofpolyolefins, polyesters, cellulose and combinations thereof.
 4. Adisposable absorbent article according to claim 3 wherein said nonwovenmaterial comprises fibers selected from the group consisting ofpolypropylene, polyethylene, polyethylene terepthalate, rayon andcombinations thereof.
 5. A disposable absorbent article according toclaim 1 wherein said nanoparticles are inorganic nanoparticles.
 6. Adisposable absorbent article according to claim 5 wherein saidnanoparticles are selected from the group consisting of titaniumdioxide, layered clay minerals, alumina oxide, silicates, andcombinations thereof.
 7. A disposable absorbent article according toclaim 6 wherein said nanoparticles are selected from the groupconsisting of titanium dioxide, Boehmite alumina, sodium magnesiumlithium fluorosilicates and combinations thereof.
 8. A disposableabsorbent article according to claim 1 wherein said hydrophilicityboosting composition further comprises a surfactant.
 9. A disposableabsorbent article according to claim 1 wherein said surfactant is anonionic surfactant.
 10. A disposable absorbent article according toclaim 1 wherein said storage layer comprises material selected from thegroup consisting of absorbent gelling material, fluff, and mixturesthereof.
 11. A disposable absorbent article according to claim 1 whereinsaid disposable absorbent article further comprises a substantiallyliquid pervious topsheet and a substantially liquid imperviousbacksheet, wherein said storage layer is between said topsheet and saidbacksheet, and at least a portion of said core wrap is between saidstorage layer and said top sheet.
 12. A disposable absorbent articleaccording to claim 1 wherein said core warp surrounds all of saidstorage layer.
 13. A disposable absorbent article according to claim 12wherein said disposable absorbent article is selected from the groupconsisting of diapers, adult incontinence products, training pant,feminine hygiene pads, and panty liners.
 14. A disposable absorbentarticle according to claim 1 wherein said substrate has been treatedwith a high-energy surface treatment.
 15. A disposable absorbent articleaccording to claim 14 wherein said high-energy surface treatment isselected from the group consisting of corona discharge treatment, plasmatreatment, UV radiation, ion beam treatment, electron beam treatment andcombinations thereof.
 16. A process for making a disposable absorbentarticle comprising an absorbent core, said absorbent core comprising astorage layer and a durable hydrophilic core wrap, said core wrapsurrounding at least a portion of said storage layer and said processcomprising the step of: coating a core wrap substrate with ahydrophilicity boosting composition, said hydrophilicity boostingcomposition comprises a hydrophilicity boosting amount of nanoparticles,wherein said nanoparticles having a particle size of from about 1 toabout 750 nanometers.
 17. A process for making a disposable absorbentarticle according to claim 16 wherein prior to or concurrent withcoating of said substrate, said substrate is treated with a high energysurface treatment said high-energy surface treatment is selected fromthe group consisting of corona discharge treatment, plasma treatment, UVradiation, ion beam treatment, electron beam treatment and combinationsthereof.
 18. A process for making a disposable absorbent articleaccording to claim 17 wherein hydrophilicity boosting compositionfurther comprises a carrier and a surfactant.
 19. A process for making adisposable absorbent article according to claim 18 wherein saidnanoparticles are inorganic nanoparticles.
 20. A process for making adisposable absorbent article according to claim 16 wherein saidsubstrate is selected from the group consisting of porous polymericfilms, nonwoven materials and combinations thereof.